In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact printer, one of the problems in the non-impact machine has been the control of the printing operation. As is well-known, the impact operation depends upon the movement of impact members, such as wires or the like, and which are typically moved by means of an electromechanical system which is believed to enable a more precise control of the impact members.
The advent of non-impact printing, as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink jet printing, in at least one form thereof, must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case of non-impact printing, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high-speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be precise and accurate from the time of formation of the droplets to depositing of such droplets on paper or like record media, and to make certain that a clean printed character results from the ink droplets. While the method of printing with ink droplets may be performed either in a continuous manner or in a demand pulse manner, the latter method is disclosed in the present application as applying the features of the present invention. The drive means for the ink droplets is generally in the form of a crystal element to provide the high-speed operation for ejecting the ink through the nozzle, while allowing time between droplets for proper operation. The ink nozzle construction must be of a nature to permit fast and clean ejection of ink droplets from the print head. Additionally, any change in direction of the flight path of ink droplets emitted from the nozzle of an ink jet printer is desirably accomplished in simple yet accurate manner whereby selected droplets may be directed to precise locations on the record media.
Representative prior art in the field of ink droplet direction control for continuous flow droplet systems includes U.S. Pat. No. 3,416,153, issued to C. H. Hertz et al. on Dec. 10, 1968, which discloses an ink jet recorder wherein a liquid jet is projected along a jet axis from a nozzle to a surface. A signal source is connected between the nozzle and a control electrode which is disposed laterally of the jet axis for providing an electric field to charge the liquid jet and to diffuse the jet into small droplets. Additionally, U.S. Pat. No. 3,596,275, issued to R. G. Sweet on July 27, 1971, discloses a fluid droplet recorder wherein a stream of writing fluid in the form of a succession of uniformly spaced droplets are charged electrostatically in accordance with signal values and then deflected electrostatically in accordance with charges carried by the droplets. Droplets may be directed to intercepting means whereby droplets so directed are not deposited on the record medium.
U.S. Pat. No. 3,737,914, issued to C. H. Hertz on June 5, 1973, discloses a liquid jet recorder wherein electrically conductive fluid is pressure-ejected through a capillary nozzle to form a jet directed toward a recording sheet. The jet nozzle is supported in an element which can be moved in side-to-side direction to vary the direction of the jet axis. U.S. Pat. No. 4,138,688, issued to R. S. Heard et al. on Feb. 6, 1979, further discloses method and apparatus for automatically controlling the inclination of patterns in ink jet printers wherein the nozzle for emitting a stream of ink drops, the charge electrode for charging the ink drops, and the deflection electrodes for deflecting the ink drops are mounted on a carrier which moves relative to the ink drop record receiving media for forming images indicative of the signals on the deflected ink drops. A voltage difference is applied across the deflection electrodes to effect electric field distortion between the electrodes to compensate for the slant due to motion of the carrier.
Representative prior art in the field of ink droplet direction control for pulse-on-demand droplet systems includes U.S. Pat. No. 3,683,212, issued to S. I. Zoltan on Aug. 8, 1972, which discloses a pulsed droplet ejecting system having a transducer coupled to liquid in a conduit which terminates in a small orifice, and wherein pressure pulses created by the transducer have sufficient amplitude to overcome the surface tension at the orifice and eject liquid droplets therefrom. Additionally, U.S. Pat. No. 3,747,120, issued to N. G. E. Stemme on July 17, 1973, discloses an arrangement for applying droplets wherein an inner chamber is provided with a fluid pressure increasing device and is connected with an outer chamber having a discharge channel through which liquid is discharged in droplet form upon short duration pressure increases.
U.S. Pat. No. 3,832,579, issued to J. P. Arndt on Aug. 27, 1974, discloses a pulsed droplet ejecting system having a transducer coupled to liquid in a conduit which terminates in a small orifice, and wherein pulses applied to the liquid send pressure waves to the orifice for causing ejection of droplets and also send pressure waves in the opposite direction against energy absorbing means. Further, U.S. Pat. No. 3,946,398, issued to E. L. Kyser et al. discloses recording apparatus which includes a writing fluid source feeding a drop projection means in the form of a pressure or deflection plate in contact with the fluid and which ejects a series of droplets of fluid from a nozzle in a discontinuous stream.
Contrary to and distinguishing from the prior art wherein the common practice in continuous flow droplet systems has been to provide ink droplet producing or deflection means between the nozzle and the record media, it is proposed to provide by the present invention an ink jet print head having improved means whereby the direction and the flight path of the ink droplets are controlled by the selective positioning and attitude of the droplet producing nozzle itself.